#!/usr/bin/env python3
"""accrual-report - Status reports for accruals

accrual-report checks accruals (postings under Assets:Receivable and
Liabilities:Payable) for errors and metadata consistency, and reports any
problems on stderr. Then it writes a report about the status of those
accruals.

If you run it with no arguments, it will generate an aging report in ODS format
in the current directory.

Otherwise, the typical way to run it is to pass an RT ticket number or
invoice link as an argument, to report about accruals that match those
criteria::

    # Report all accruals associated with RT#1230:
    accrual-report 1230
    # Report all accruals with the invoice link rt:45/670.
    accrual-report 45/670
    # Report all accruals with the invoice link Invoice980.pdf.
    accrual-report Invoice980.pdf

By default, to stay fast, accrual-report only looks for postings from the
beginning of the last fiscal year. You can search further back in history
by passing the ``--since`` argument. The argument can be a fiscal year, or
a negative number of how many years back to search::

    # Search for accruals since 2016
    accrual-report --since 2016 [search terms …]
    # Search for accruals from the beginning of three fiscal years ago
    accrual-report --since -3 [search terms …]

If you want to further limit what accruals are reported, you can match on
other metadata by passing additional arguments in ``name=value`` format.
You can pass any number of search terms. For example::

    # Report accruals associated with RT#1230 and Jane Doe
    accrual-report 1230 entity=Doe-Jane

accrual-report will automatically decide what kind of report to generate
from the search terms you provide and the results they return. If you pass
no search terms, it generates an aging report. If your search terms match a
single outstanding payable, it writes an outgoing approval report.
Otherwise, it writes a basic balance report. You can specify what report
type you want with the ``--report-type`` option::

    # Write an outgoing approval report for all outstanding accruals for
    # Jane Doe, even if there's more than one
    accrual-report --report-type outgoing entity=Doe-Jane
    # Write an aging report for a specific project
    accrual-report --report-type aging project=ProjectName
"""
# Copyright © 2020  Brett Smith
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

import argparse
import collections
import datetime
import enum
import logging
import sys

from pathlib import Path

from typing import (
    cast,
    Any,
    BinaryIO,
    Callable,
    Iterable,
    Iterator,
    List,
    Mapping,
    NamedTuple,
    Optional,
    Sequence,
    Set,
    TextIO,
    Tuple,
    TypeVar,
    Union,
)
from ..beancount_types import (
    Entries,
    Error,
    Errors,
    MetaKey,
    MetaValue,
    Transaction,
)

import odf.style  # type:ignore[import]
import odf.table  # type:ignore[import]
import rt

from beancount.parser import printer as bc_printer

from . import core
from .. import books
from .. import cliutil
from .. import config as configmod
from .. import data
from .. import filters
from .. import rtutil

PROGNAME = 'accrual-report'

PostGroups = Mapping[Optional[str], 'AccrualPostings']
T = TypeVar('T')

logger = logging.getLogger('conservancy_beancount.reports.accrual')

class Sentinel:
    pass


class Account(NamedTuple):
    name: str
    aging_thresholds: Sequence[int]


class AccrualAccount(enum.Enum):
    # Note the aging report uses the same order accounts are defined here.
    # See AgingODS.start_spreadsheet().
    RECEIVABLE = Account('Assets:Receivable', [365, 120, 90, 60])
    PAYABLE = Account('Liabilities:Payable', [365, 90, 60, 30])

    @classmethod
    def account_names(cls) -> Iterator[str]:
        return (acct.value.name for acct in cls)

    @classmethod
    def by_account(cls, name: data.Account) -> 'AccrualAccount':
        for account in cls:
            if name.is_under(account.value.name):
                return account
        raise ValueError(f"unrecognized account {name!r}")

    @classmethod
    def classify(cls, related: core.RelatedPostings) -> 'AccrualAccount':
        for account in cls:
            account_name = account.value.name
            if all(post.account.is_under(account_name) for post in related):
                return account
        raise ValueError("unrecognized account set in related postings")

    @property
    def normalize_amount(self) -> Callable[[T], T]:
        return core.normalize_amount_func(self.value.name)


class AccrualPostings(core.RelatedPostings):
    __slots__ = (
        'accrual_type',
        'end_balance',
        'account',
        'entity',
        'invoice',
    )
    INCONSISTENT = Sentinel()

    def __init__(self,
                 source: Iterable[data.Posting]=(),
                 *,
                 _can_own: bool=False,
    ) -> None:
        super().__init__(source, _can_own=_can_own)
        self.account = self._single_item(post.account for post in self)
        if isinstance(self.account, Sentinel):
            self.accrual_type: Optional[AccrualAccount] = None
            norm_func: Callable[[T], T] = lambda x: x
            entity_pred: Callable[[data.Posting], bool] = bool
        else:
            self.accrual_type = AccrualAccount.by_account(self.account)
            norm_func = self.accrual_type.normalize_amount
            entity_pred = lambda post: norm_func(post.units).number > 0
        self.entity = self._single_item(self.entities(entity_pred))
        self.invoice = self._single_item(self.first_meta_links('invoice', None))
        self.end_balance = norm_func(self.balance_at_cost())

    def _single_item(self, seq: Iterable[T]) -> Union[T, Sentinel]:
        items = iter(seq)
        try:
            item1 = next(items)
        except StopIteration:
            all_same = False
        else:
            all_same = all(item == item1 for item in items)
        return item1 if all_same else self.INCONSISTENT

    def entities(self, pred: Callable[[data.Posting], bool]=bool) -> Iterator[MetaValue]:
        return filters.iter_unique(
            post.meta['entity']
            for post in self
            if pred(post) and 'entity' in post.meta
        )

    def make_consistent(self) -> Iterator[Tuple[str, 'AccrualPostings']]:
        account_ok = isinstance(self.account, str)
        entity_ok = isinstance(self.entity, str)
        # `'/' in self.invoice` is just our heuristic to ensure that the
        # invoice metadata is "unique enough," and not just a placeholder
        # value like "FIXME". It can be refined if needed.
        invoice_ok = isinstance(self.invoice, str) and '/' in self.invoice
        if account_ok and entity_ok and invoice_ok:
            # type ignore for <https://github.com/python/mypy/issues/6670>
            yield (self.invoice, self)  # type:ignore[misc]
            return
        groups = collections.defaultdict(list)
        for post in self:
            post_invoice = self.invoice if invoice_ok else (
                post.meta.get('invoice') or 'BlankInvoice'
            )
            post_entity = self.entity if entity_ok else (
                post.meta.get('entity') or 'BlankEntity'
            )
            groups[f'{post.account} {post_invoice} {post_entity}'].append(post)
        type_self = type(self)
        for group_key, posts in groups.items():
            yield group_key, type_self(posts, _can_own=True)

    def is_paid(self, default: Optional[bool]=None) -> Optional[bool]:
        if self.accrual_type is None:
            return default
        else:
            return self.end_balance.le_zero()

    def is_zero(self, default: Optional[bool]=None) -> Optional[bool]:
        if self.accrual_type is None:
            return default
        else:
            return self.end_balance.is_zero()

    def since_last_nonzero(self) -> 'AccrualPostings':
        for index, (post, balance) in enumerate(self.iter_with_balance()):
            if balance.is_zero():
                start_index = index
        try:
            empty = start_index == index
        except NameError:
            empty = True
        return self if empty else self[start_index + 1:]

    @property
    def rt_id(self) -> Union[str, None, Sentinel]:
        return self._single_item(self.first_meta_links('rt-id', None))


class BaseReport:
    def __init__(self, out_file: TextIO) -> None:
        self.out_file = out_file
        self.logger = logger.getChild(type(self).__name__)

    def _report(self, posts: AccrualPostings, index: int) -> Iterable[str]:
        raise NotImplementedError("BaseReport._report")

    def run(self, groups: PostGroups) -> None:
        for index, invoice in enumerate(groups):
            for line in self._report(groups[invoice], index):
                print(line, file=self.out_file)


class AgingODS(core.BaseODS[AccrualPostings, Optional[data.Account]]):
    DOC_COLUMNS = [
        'rt-id',
        'invoice',
        'approval',
        'contract',
        'purchase-order',
    ]
    COLUMNS = [
        'Date',
        data.Metadata.human_name('entity'),
        'Invoice Amount',
        'Booked Amount',
        data.Metadata.human_name('project'),
        *(data.Metadata.human_name(key) for key in DOC_COLUMNS),
    ]
    COL_COUNT = len(COLUMNS)

    def __init__(self,
                 rt_wrapper: rtutil.RT,
                 date: datetime.date,
                 logger: logging.Logger,
    ) -> None:
        super().__init__(rt_wrapper)
        self.date = date
        self.logger = logger

    def init_styles(self) -> None:
        super().init_styles()
        self.style_widecol = self.replace_child(
            self.document.automaticstyles,
            odf.style.Style,
            name='WideCol',
        )
        self.style_widecol.setAttribute('family', 'table-column')
        self.style_widecol.addElement(odf.style.TableColumnProperties(
            columnwidth='1.25in',
        ))

    def section_key(self, row: AccrualPostings) -> Optional[data.Account]:
        if isinstance(row.account, str):
            return row.account
        else:
            return None

    def start_spreadsheet(self) -> None:
        for accrual_type in AccrualAccount:
            self.use_sheet(accrual_type.name.title())
            for index in range(self.COL_COUNT):
                stylename = self.style_widecol if index else ''
                self.sheet.addElement(odf.table.TableColumn(stylename=stylename))
            self.add_row(*(
                self.string_cell(name, stylename=self.style_bold)
                for name in self.COLUMNS
            ))
            self.lock_first_row()

    def start_section(self, key: Optional[data.Account]) -> None:
        if key is None:
            return
        self.age_thresholds = list(AccrualAccount.by_account(key).value.aging_thresholds)
        self.age_balances = [core.MutableBalance() for _ in self.age_thresholds]
        accrual_date = self.date - datetime.timedelta(days=self.age_thresholds[-1])
        acct_parts = key.slice_parts()
        self.use_sheet(acct_parts[1])
        self.add_row()
        self.add_row(self.string_cell(
            f"{' '.join(acct_parts[2:])} {acct_parts[1]} Aging Report"
            f" Accrued by {accrual_date.isoformat()} Unpaid by {self.date.isoformat()}",
            stylename=self.merge_styles(self.style_bold, self.style_centertext),
            numbercolumnsspanned=self.COL_COUNT,
        ))
        self.add_row()

    def end_section(self, key: Optional[data.Account]) -> None:
        if key is None:
            return
        total_balance = core.MutableBalance()
        text_style = self.merge_styles(self.style_bold, self.style_endtext)
        text_span = 4
        last_age_text: Optional[str] = None
        self.add_row()
        for threshold, balance in zip(self.age_thresholds, self.age_balances):
            years, days = divmod(threshold, 365)
            years_text = f"{years} {'Year' if years == 1 else 'Years'}"
            days_text = f"{days} Days"
            if years and days:
                age_text = f"{years_text} {days_text}"
            elif years:
                age_text = years_text
            else:
                age_text = days_text
            if last_age_text is None:
                age_range = f"Over {age_text}"
            else:
                age_range = f"{age_text}–{last_age_text}"
            self.add_row(
                self.string_cell(
                    f"Total Aged {age_range}: ",
                    stylename=text_style,
                    numbercolumnsspanned=text_span,
                ),
                *(odf.table.TableCell() for _ in range(1, text_span)),
                self.balance_cell(balance),
            )
            last_age_text = age_text
            total_balance += balance
        self.add_row(
            self.string_cell(
                "Total Unpaid: ",
                stylename=text_style,
                numbercolumnsspanned=text_span,
            ),
            *(odf.table.TableCell() for _ in range(1, text_span)),
            self.balance_cell(total_balance),
        )

    def write_row(self, row: AccrualPostings) -> None:
        age = (self.date - row[0].meta.date).days
        if row.end_balance.ge_zero():
            for index, threshold in enumerate(self.age_thresholds):
                if age >= threshold:
                    self.age_balances[index] += row.end_balance
                    break
            else:
                return
        raw_balance = row.balance()
        if row.accrual_type is not None:
            raw_balance = row.accrual_type.normalize_amount(raw_balance)
        if raw_balance == row.end_balance:
            amount_cell = odf.table.TableCell()
        else:
            amount_cell = self.balance_cell(raw_balance)
        projects = {post.meta.get('project') or None for post in row}
        projects.discard(None)
        self.add_row(
            self.date_cell(row[0].meta.date),
            self.multiline_cell(row.entities()),
            amount_cell,
            self.balance_cell(row.end_balance),
            self.multiline_cell(sorted(projects)),
            *(self.meta_links_cell(row.all_meta_links(key))
              for key in self.DOC_COLUMNS),
        )


class AgingReport(BaseReport):
    def __init__(self,
                 rt_wrapper: rtutil.RT,
                 out_file: BinaryIO,
                 date: Optional[datetime.date]=None,
    ) -> None:
        if date is None:
            date = datetime.date.today()
        self.out_bin = out_file
        self.logger = logger.getChild(type(self).__name__)
        self.ods = AgingODS(rt_wrapper, date, self.logger)

    def run(self, groups: PostGroups) -> None:
        rows: List[AccrualPostings] = []
        for group in groups.values():
            if group.is_zero():
                # Cheap optimization: don't slice and dice groups we're not
                # going to report anyway.
                continue
            elif group.accrual_type is None:
                group = group.since_last_nonzero()
            else:
                # Filter out new accruals after the report date.
                # e.g., cover the case that the same invoices has multiple
                # postings over time, and we don't want to report too-recent
                # ones.
                cutoff_date = self.ods.date - datetime.timedelta(
                    days=group.accrual_type.value.aging_thresholds[-1],
                )
                group = AccrualPostings(
                    post for post in group.since_last_nonzero()
                    if post.meta.date <= cutoff_date
                    or group.accrual_type.normalize_amount(post.units.number) < 0
                )
            if group and not group.is_zero():
                rows.append(group)
        rows.sort(key=lambda related: (
            related.account,
            related[0].meta.date,
            ('\0'.join(related.entities())
             if related.entity is related.INCONSISTENT
             else related.entity),
        ))
        self.ods.write(rows)
        self.ods.save_file(self.out_bin)


class BalanceReport(BaseReport):
    def _report(self, posts: AccrualPostings, index: int) -> Iterable[str]:
        posts = posts.since_last_nonzero()
        date_s = posts[0].meta.date.strftime('%Y-%m-%d')
        if index:
            yield ""
        yield f"{posts.invoice}:"
        yield f"  {posts.balance_at_cost()} outstanding since {date_s}"


class OutgoingReport(BaseReport):
    def __init__(self, rt_wrapper: rtutil.RT, out_file: TextIO) -> None:
        super().__init__(out_file)
        self.rt_wrapper = rt_wrapper
        self.rt_client = rt_wrapper.rt

    def _primary_rt_id(self, posts: AccrualPostings) -> rtutil.TicketAttachmentIds:
        rt_id = posts.rt_id
        if rt_id is None:
            raise ValueError("no rt-id links found")
        elif isinstance(rt_id, Sentinel):
            raise ValueError("multiple rt-id links found")
        parsed = rtutil.RT.parse(rt_id)
        if parsed is None:
            raise ValueError("rt-id is not a valid RT reference")
        else:
            return parsed

    def _report(self, posts: AccrualPostings, index: int) -> Iterable[str]:
        posts = posts.since_last_nonzero()
        try:
            ticket_id, _ = self._primary_rt_id(posts)
            ticket = self.rt_client.get_ticket(ticket_id)
            # Note we only use this when ticket is None.
            errmsg = f"ticket {ticket_id} not found"
        except (ValueError, rt.RtError) as error:
            ticket = None
            errmsg = error.args[0]
        if ticket is None:
            self.logger.error(
                "can't generate outgoings report for %s because no RT ticket available: %s",
                posts.invoice, errmsg,
            )
            return

        try:
            rt_requestor = self.rt_client.get_user(ticket['Requestors'][0])
        except (IndexError, rt.RtError):
            rt_requestor = None
        if rt_requestor is None:
            requestor = ''
            requestor_name = ''
        else:
            requestor_name = (
                rt_requestor.get('RealName')
                or ticket.get('CF.{payment-to}')
                or ''
            )
            requestor = f'{requestor_name} <{rt_requestor["EmailAddress"]}>'.strip()

        balance_s = posts.end_balance.format(None)
        raw_balance = -posts.balance()
        if raw_balance != posts.end_balance:
            balance_s = f'{raw_balance} ({balance_s})'

        contract_links = list(posts.all_meta_links('contract'))
        if contract_links:
            contract_s = ' , '.join(self.rt_wrapper.iter_urls(
                contract_links, missing_fmt='<BROKEN RT LINK: {}>',
            ))
        else:
            contract_s = "NO CONTRACT GOVERNS THIS TRANSACTION"
        projects = [v for v in posts.meta_values('project')
                    if isinstance(v, str)]

        yield "PAYMENT FOR APPROVAL:"
        yield f"REQUESTOR: {requestor}"
        yield f"TOTAL TO PAY: {balance_s}"
        yield f"AGREEMENT: {contract_s}"
        yield f"PAYMENT TO: {ticket.get('CF.{payment-to}') or requestor_name}"
        yield f"PAYMENT METHOD: {ticket.get('CF.{payment-method}', '')}"
        yield f"PROJECT: {', '.join(projects)}"
        yield "\nBEANCOUNT ENTRIES:\n"

        last_txn: Optional[Transaction] = None
        for post in posts:
            txn = post.meta.txn
            if txn is not last_txn:
                last_txn = txn
                txn = self.rt_wrapper.txn_with_urls(txn, '{}')
                yield bc_printer.format_entry(txn)


class ReportType(enum.Enum):
    AGING = AgingReport
    BALANCE = BalanceReport
    OUTGOING = OutgoingReport
    AGE = AGING
    BAL = BALANCE
    OUT = OUTGOING
    OUTGOINGS = OUTGOING

    @classmethod
    def by_name(cls, name: str) -> 'ReportType':
        try:
            return cls[name.upper()]
        except KeyError:
            raise ValueError(f"unknown report type {name!r}") from None


class ReturnFlag(enum.IntFlag):
    LOAD_ERRORS = 1
    # 2 was used in the past, it can probably be reclaimed.
    REPORT_ERRORS = 4
    NOTHING_TO_REPORT = 8


def filter_search(postings: Iterable[data.Posting],
                  search_terms: Iterable[cliutil.SearchTerm],
) -> Iterable[data.Posting]:
    accounts = tuple(AccrualAccount.account_names())
    postings = (post for post in postings if post.account.is_under(*accounts))
    for query in search_terms:
        postings = query.filter_postings(postings)
    return postings

def parse_arguments(arglist: Optional[Sequence[str]]=None) -> argparse.Namespace:
    parser = argparse.ArgumentParser(prog=PROGNAME)
    cliutil.add_version_argument(parser)
    parser.add_argument(
        '--report-type', '-t',
        metavar='NAME',
        type=ReportType.by_name,
        help="""The type of report to generate, one of `aging`, `balance`, or
`outgoing`. If not specified, the default is `aging` when no search terms are
given, `outgoing` for search terms that return a single outstanding payable,
and `balance` any other time.
""")
    parser.add_argument(
        '--since',
        metavar='YEAR',
        type=int,
        default=-1,
        help="""How far back to search the books for related transactions.
You can either specify a fiscal year, or a negative offset from the current
fiscal year, to start loading entries from. The default is -1 (start from the
previous fiscal year).
""")
    parser.add_argument(
        '--output-file', '-O',
        metavar='PATH',
        type=Path,
        help="""Write the report to this file, or stdout when PATH is `-`.
The default is stdout for the balance and outgoing reports, and a generated
filename for other reports.
""")
    cliutil.add_loglevel_argument(parser)
    parser.add_argument(
        'search_terms',
        metavar='FILTER',
        type=cliutil.SearchTerm.arg_parser('invoice', 'rt-id'),
        nargs=argparse.ZERO_OR_MORE,
        help="""Report on accruals that match this criteria. The format is
NAME=TERM. TERM is a link or word that must exist in a posting's NAME
metadata to match. A single ticket number is a shortcut for
`rt-id=rt:NUMBER`. Any other link, including an RT attachment link in
`TIK/ATT` format, is a shortcut for `invoice=LINK`.
""")
    args = parser.parse_args(arglist)
    if args.report_type is None and not args.search_terms:
        args.report_type = ReportType.AGING
    return args

def main(arglist: Optional[Sequence[str]]=None,
         stdout: TextIO=sys.stdout,
         stderr: TextIO=sys.stderr,
         config: Optional[configmod.Config]=None,
) -> int:
    args = parse_arguments(arglist)
    cliutil.set_loglevel(logger, args.loglevel)
    if config is None:
        config = configmod.Config()
        config.load_file()

    returncode = 0
    books_loader = config.books_loader()
    if books_loader is None:
        entries, load_errors, _ = books.Loader.load_none(config.config_file_path())
    elif args.report_type is ReportType.AGING:
        entries, load_errors, _ = books_loader.load_all()
    else:
        entries, load_errors, _ = books_loader.load_all(args.since)
    filters.remove_opening_balance_txn(entries)
    for error in load_errors:
        bc_printer.print_error(error, file=stderr)
        returncode |= ReturnFlag.LOAD_ERRORS

    postings = list(filter_search(
        data.Posting.from_entries(entries), args.search_terms,
    ))
    if not postings:
        logger.warning("no matching entries found to report")
        returncode |= ReturnFlag.NOTHING_TO_REPORT
    # groups is a mapping of metadata value strings to AccrualPostings.
    # The keys are basically arbitrary, the report classes don't rely on them,
    # but they do help symbolize what's being grouped.
    # For the outgoing approval report, groups maps rt-id link strings to
    # associated accruals.
    # For all other reports, groups starts by grouping postings together by
    # invoice link string, then uses AccrualReport.make_consistent() to split
    # out groups that need it.
    groups: PostGroups
    if args.report_type is None or args.report_type is ReportType.OUTGOING:
        groups = dict(AccrualPostings.group_by_first_meta_link(postings, 'rt-id'))
        if (args.report_type is None
            and len(groups) == 1
            and all(group.accrual_type is AccrualAccount.PAYABLE
                    and not group.is_paid()
                    and key  # Make sure we have a usable rt-id
                    for key, group in groups.items())
        ):
            args.report_type = ReportType.OUTGOING
    if args.report_type is not ReportType.OUTGOING:
        groups = {
            key: group
            for _, source in AccrualPostings.group_by_first_meta_link(postings, 'invoice')
            for key, group in source.make_consistent()
        }
    if args.report_type is not ReportType.AGING:
        groups = {
            key: posts for key, posts in groups.items() if not posts.is_paid()
        } or groups
    del postings

    report: Optional[BaseReport] = None
    output_path: Optional[Path] = None
    if args.report_type is ReportType.AGING:
        rt_wrapper = config.rt_wrapper()
        if rt_wrapper is None:
            logger.error("unable to generate aging report: RT client is required")
        else:
            now = datetime.datetime.now()
            if args.output_file is None:
                out_dir_path = config.repository_path() or Path()
                args.output_file = out_dir_path / now.strftime('AgingReport_%Y-%m-%d_%H:%M.ods')
                logger.info("Writing report to %s", args.output_file)
            out_bin = cliutil.bytes_output(args.output_file, stdout)
            report = AgingReport(rt_wrapper, out_bin)
    elif args.report_type is ReportType.OUTGOING:
        rt_wrapper = config.rt_wrapper()
        if rt_wrapper is None:
            logger.error("unable to generate outgoing report: RT client is required")
        else:
            out_file = cliutil.text_output(args.output_file, stdout)
            report = OutgoingReport(rt_wrapper, out_file)
    else:
        out_file = cliutil.text_output(args.output_file, stdout)
        report = BalanceReport(out_file)

    if report is None:
        returncode |= ReturnFlag.REPORT_ERRORS
    else:
        report.run(groups)
    return 0 if returncode == 0 else 16 + returncode

entry_point = cliutil.make_entry_point(__name__, PROGNAME)

if __name__ == '__main__':
    exit(entry_point())